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Volume 26 (1980)
- Issue 4 Pages 227-
- Issue 3 Pages 137-
- Issue 2 Pages 75-
- Issue 1 Pages 1-
Volume 26, Issue 1
Displaying 1-6 of 6 articles from this issue
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Ryuichi SHICHI, Takashi OKUDA, Shigeo YOSHIOKA1980 Volume 26 Issue 1 Pages 1-16
Published: May 30, 1980
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSA moving float type water-tube tiltmeter is designed for a reliable continuous record ing of secular ground tilt and earth tide observations. It is aimed in the present design that the detector should have such features as a wide dynamic range, a high resolution, an easy and secure calibration device, and very small mechanical drift. These are achieved by improving several defects associated with moving float type water-tube tiltmeters that have so far been developed. The diminishing effect, the difference between float movement and water level change, is markedly decreased by the adoption of a weak cross spring suspension for the fulcrum and a reduced mechanical magnification to decrease suction effect of the sensor. The diminishing factor in the present design, which is experimentally determined, is as small as less than 1%. A knife edge joint for connecting float rod to the arm can minimize the torque due to unbarance of the float metacenter which may cause spring creep or mechanical drift of the detector. Setting the hinge of calibration arm on the same axis of the fulcrum of the float arm, we can keep a constant sensitivity for a wide range, by which a highly reliable calibration is possible. Conversion coefficient for water level change has been obtained in a good ac curacy by this calibration mechanism. Although some errors (±2% at maximum) might be inherent in the case of absolute calibration, the relative accuracy between detectors has been found to be excellent under the routine observation.View full abstractDownload PDF (1542K) -
-Amplitude Characteristics-Hiroshi ISHII, Toshiya SATO, Akio TAKAGI1980 Volume 26 Issue 1 Pages 17-25
Published: May 30, 1980
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSThe amplitude characteristics of migrating strain are investigated making an analysis of the data from extensometers in five crustal movement observatories located in the northeastern Japan arc. It is revealed that the larger the amplitude of annual strain becomes, the larger the amplitude of migrating strain and secular strain becomes. Further, it is found that the amplitude ratio of annual strain to migrating and secular strain versus analyzed period divided by degree of Chebychev approximation function (approximately corresponding to wave length) forms in line.View full abstractDownload PDF (749K) -
Hironori TSUKAMOTO, Ichiro NAKAGAWA1980 Volume 26 Issue 1 Pages 26-34
Published: May 30, 1980
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSEffects of oceanic tides on tidal variations of gravity at Kyoto and Mizusawa, in Japan, were estimated for two principal semidiurnal constituents, M2 and S2. In the estimation, tidal charts newly drawn by the present authors were used for the seas adjacent to Japan. For the global ocean, three and two models were employed for M2 and S2 constituents, respectively. As for M2 constituent, estimated values of the oceanic effect change mainly with the global tidal model employed. This suggests an incompleteness of the global tidal models. As for S2 constituent, it will be necessary to take meteorological disturbances and atmospheric tides in more detail as well as the oceanic effect into consideration, for the further discussion.View full abstractDownload PDF (922K) -
Tadahiro SATO, Masatsugu OOE, Norio SATO1980 Volume 26 Issue 1 Pages 35-49
Published: May 30, 1980
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSThe tidal strain has been observed at Esashi Earth Tides Station which designed for earth tides observations. The station is located in the middle of Mt. Abara (780 m above mean sea level). Three extensometers made of quartz tubes 30 mm in diameter and 36, 36 and 51 m in length are installed in the vault in NS, EW and NW directions respectively. The detector of these extensometers is a differential transformer. Routine observations were begun in June 1979. Preliminary records from the end of April 1979 to the begining of June 1979 show the drifts of 4X10-8/month for NS and EW components and 2X10-8 for NW component. These drifts are probably of instrumental origin. The data of NS and EW components for the period during June to August 1979 are analyzed in two steps. The first one is the estimations of the amplitudes, their factors and phase differences of the observed data by least square fitting to the theoretical strain waves which are derived from the potential developed by Cartwright, Tayler and Edden. In these analysis the drift and non-tidal variations are removed by using Pertzev's filter. The standard deviation of a single observation has been found to be 2X10-8 in both components, which exceeds about 70 times the value as compared with the accuracy of the calibrations of the instruments or the reading errors. The second is the analysis of residuals obtained by subtracting the above estimated tidal strain waves from the original data. These residuals show broad shaped power spectra at the tidal bands and high powers at the low frequency band. The AR-response method is applied to the ahalysis of the relations between the residuals and the changes of the atmospheric pressure. The results suggest the existences of coupling between them but the physical interpretation is a problem of further investigations.View full abstractDownload PDF (2379K) -
Kasio ISIKAWA1980 Volume 26 Issue 1 Pages 50-58
Published: May 30, 1980
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSThe problem of geomagnetic secular variation at Kanozan has been reported already by the author. In this report, the geomagnetic monthly mean values of Kanozan Geodetic Observatory were compared with those of the other observatories (Memanbetsu, Mizusawa, Kakioka and Kanoya), during the period from Jan . 1961 to Dec. 1979. From the results, it seems that the secular variations of differences of the geomagnetic field between Kanozan and other observatories are larger than its normal values .View full abstractDownload PDF (592K) -
Yoshibumi TOMODA, Hiromi FUJIMOTO1980 Volume 26 Issue 1 Pages 59-65
Published: May 30, 1980
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSA new method is proposed for determination of both the magnetization of a vessel and geomagnetic daily variation by use of towing three proton magnetometers. Results of simulation show that geomagnetic daily variation can be measured within accuracy of 6±1 nT, if three precision proton magnetometers are towed 1300 m, 700 m, 100 m, apart from the vessel, measurement being carried out with accuracy of±0.05 n T every 2 min with ship's speed of 10 knots, and if accuracy of relative position fixing of the vessel is better than ±8 m in an hour.View full abstractDownload PDF (707K)
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